This invention relates to input-output converters and in particular to an interface for use in communications systems having terminals that utilized different logic voltage levels and character formats.
Communications systems that transmit and receive digital data are frequently integrated with terminals and transmitting and receiving equipment that function at different logic voltage levels and utilize different character formats. A typical example of such an arrangement is the Modular AUTODIN Interface Device (MAID) which operates into the local teletype terminal equipments at European NATO installations. The MAID UNIT supervises a coordinated operation with the European Automatic Digital Network (Autodin). The requirement in this particular instance is an input-output converter that accomplishes all the necessary logic voltage level and format conversions and generates the essential handshaking signal to permit the exchange of information between the MAID unit and three terminal units: a Transtel Model AH Printer, a Siemens Model 158 paper tape punch and a Siemons Model 38 Paper Tape Reader. Incoming 5 level serial asynchronous data with start-stop frame bits from the MAID must be converted to the correct logic level and polarity and forwarded to the printer for output. The asynchronous start-stop framing bits must then be removed from the five data bits and the character output in character parallel format to the paper tape punch with corresponding strobe signals. Character parallel data for outputting, which originates at the tape reader, must be sent to the converter for framing with the asynchronous start/stop bits and sent serially to the MAID at the correct logic voltage level. It is also required that the input-output converter respond to a "clear to send" command from this MAID for control of output information and provide a "ready" level to the MAID and an "enable" signal to the reader.
The present invention is directed toward providing an input-output converter that can accomplish all of these functions and that can be readily adapted to various other similar applications.